1. Field of the Invention
The present invention relates to a finishing method for a fiber surface fastener in which a plurality of engaging elements are formed on a surface of a foundation cloth composed of woven fabric or nonwoven fabric and a fiber surface fastener obtained by the same finishing method.
2. Description of the Prior Art
In a surface fastener which is formed by knitting or weaving monofilament and/or multi-filament in a loop shape at the same time when the foundation cloth is knitted or woven, and in which a plurality of hook-like or loop-like engaging elements are formed on the foundation cloth face, if engagement/disengagement of said surface fastener is repeated without any special finish processing, the loop-like engaging elements are loosened inside a knitting/weaving structure of the foundation cloth so that the hook-like engaging elements come to slip out easily, thereby the engaging/disengaging function as a surface fastener being lost. In order to prevent such loss of the engaging/disengaging function, a surface opposite to a surface on which engaging elements of the foundation cloth are formed is coated with thermoplastic resin, so as to fix the knitting/weaving structure of the foundation cloth while the base portions of the engaging elements are fixed to the foundation cloth, the procedure generally being called back-coating.
Upon this back-coating, as disclosed in, for example, Japanese Utility Model Application Publication No. 3-8388, the foundation cloth of an elongated surface fastener is carried on a predetermined passage with its rear surface directed upward and, at a resin coating portion, a liquid-state coating material is poured from a coater having a doctor plate and a coating material is applied to the foundation cloth with an uniform thickness. Or, as disclosed in Japanese Utility Model Application Publication No. 4-14149, a surface fastener is carried with a coating face of a surface fastener in contact with a surface of a rotary roll whose bottom portion is dipped in a coating bath, so that that foundation cloth is coated with coating material.
On the other hand, the surface fasteners of this kind do not necessarily have engaging elements on only one surface of the foundation cloth. There are surface fasteners having engaging elements formed on both front and rear surfaces of the foundation cloth. Generally, when the engaging elements are formed on both of the front and rear surfaces of the foundation cloth, the hook-like male engaging elements are formed on one face while the loop-like female engaging elements are formed on the other face. Applying coating materials to such double-face surface fasteners is impossible by the coating methods disclosed in the above publications.
Accordingly, as disclosed in, for example, Japanese Patent Application Laid-Open No. 4-49904, resin whose 100% modulus is 60 kg/cm2 or less is applied to an engaging element formation surface of the surface fastener in the form of solution or emulsion having the viscosity of 50 to 2000 centi poise with an air spray method and is dried in order to fix the surface fastener having the engaging elements to both of the front and rear surfaces of the foundation cloth. According to this coating method, fixing of knitting/weaving structure of the foundation cloth and fixing of the engaging elements to the foundation cloth can be achieved without losing softness of the surface fastener and penetration of a needle upon sewing operation is never inhibited.
Although coating by pouring down coating agent or coating through a roller as proposed by the above-described Japanese Utility Model Application Publication No. 3-8388 and Japanese Utility Model Application Publication No. 4-14149 are valid for a surface fastener in which the engaging elements are formed on only a single surface of the foundation cloth, not only the coating to the double-face surface fastener as described above is impossible, but also the application amount of the coating agent is inevitably increased and resin film is formed on its coating surface, so that resistance on a needle pierced upon sewing tends to increase.
On the other hand, although coating can be applied to the double-face surface by the coating method proposed in the above-described Japanese Patent Application Laid-Open No. 4-49904, part of the coating agent inevitably adheres to the engaging elements themselves and solidifies thereby inhibiting smooth engagement/disengagement function. Particularly, multi-filament is used for the loop-like female engaging elements and such female engaging elements require to be so constructed that respective filaments are sufficiently separated while front ends thereof are widened so as to be kept apart from each other in order to achieve engagement with and disengagement from the mating hook-like male engaging elements accurately. If coating is applied to the female engaging elements having such a structure with the airless spray method, not only coating agent adheres between the multi-filaments so that they are bonded and solidified, but also thin films may be formed on loops and further, it is difficult to feed the coating agent effectively up to the foundation cloth located at the base portions of the engaging elements.
The present invention has been achieved to solve the above-described conventional problems. More specifically, an object of the present invention is to provide a finishing method for obtaining a fiber surface fastener through a simple process, which is capable of, irrespective of the configuration of the engaging elements or the front/rear surfaces of the foundation cloth, accurately fixing the entangling portion between the foundation cloth composed of knitted/woven fabric or nonwoven fabric and the base portion of the engaging elements, and the entangling portion between yarns in the foundation cloth, that is, the entangling portion between fibers in the knitting/weaving structure of knitted/woven fabric or in base material of nonwoven fabric, and the entangling portion between a fiber in the base material and a loop fiber. Further, the finishing method is capable of inhibiting the coating agent from adhering to or solidifying on the surface of a protruded portion of the engaging element, reducing the entire amount of the coating agent used and obtaining a fiber surface fastener excellent in softness, thereby producing no obstacle in sewing processing and allowing the engaging elements to engage/disengage smoothly. Further, another object of the present invention is to provide a fiber surface fastener which is obtained according to the same finishing method.
This invention regards to a finishing method for fixing a fiber surface fastener including a plurality of engaging elements on a foundation cloth composed of knitted/woven cloth or nonwoven cloth using synthetic resin. The finishing method is characterized by comprising: carrying the surface fastener continuously; applying powdery hot-melt adhesive to the engaging-element-formation face of the carried surface fastener from a separate position; heating the surface fastener to which the powdery hot-melt adhesive is applied at a temperature not lower than the melting temperature of the adhesive for a required time so as to melt the applied adhesive; and cooling the surface fastener after the heating time elapses.
The hot-melt adhesive mentioned here is solid under normal temperatures and 100% of its component is solid compound mainly made of thermoplastic resin. Usually, the adhesive is melted inside an applicator by heating, and applied to and pressed against an object. Adhesion is completed several seconds after pressing. Examples of the thermoplastic resin, a main component of this hot-melt adhesive, are ethylene vinyl acetate copolymer, polyethylene, a tactic polypropylene, ethylene acrylate copolymer, saturated copolymerized nylon, saturated copolymerized polyester.
Usually, this kind of hot-melt adhesive is provided with tackifier which is soluble with thermoplastic resin, a main component of the adhesive, so as to provide adhesive with hot tack performance, and with wax, which lowers viscosity of adhesive. As the tackifier, rosin and rosin derivative, pinene base resin, or oil base carbon hydride resin are used. As wax, ordinarily, paraffin wax, microcrystalline wax, low molecular PE wax, Fisher/toropushe wax, modified wax, alpha olefin wax and the like are often used.
According to the present invention, preliminarily set amount of powdery hot-melt adhesive having such a composition is applied to the engaging element formation face of an elongated surface fastener which is composed of knitted/woven cloth or nonwoven cloth and carried continuously. This application is carried out, for example, through a roller with grooves which is rotated at a predetermined rotation speed so as to spray the powdery hot-melt adhesive charged in a hopper. The application amount is controlled by changing the rotation speed of the roller with grooves and the size of the grooves. Because the hot-melt adhesive sprayed is powdery, the hot-melt adhesive gathers at the base portion of each engaging element and on the surface of the foundation cloth due to vibration and the like during conveyance, so that the adhesive substantially never adheres to the engaging elements themselves, not only in the hook-like male engaging elements but also in the female engaging elements composed of a plurality of the loop-like filaments.
By heating the surface fastener applied with the hot-melt adhesive, only the hot-melt adhesive is melted. The viscosity at this time is desired to be low to keep high diffusibility of the adhesive. The melted hot-melt adhesive gathers mainly at entangling portions between the engaging elements and the foundation cloth, and entangling portions between fibers of the foundation cloth in case of knitted/woven fabric or entangling portions between the fibers of the foundation cloth and the loop fibers in case of nonwoven fabric. After the surface fastener passes a heating region, it is conveyed to a cooling region. Cooling at this cooling region can be carried out, for example, by feeding cool air actively, but it can also be carried out by self-cooling. The melted hot-melt adhesive is solidified by cooling so that it fixes the knitting/weaving structure of the foundation cloth or the entangling portions of the fibers and further fixes the entangling portions between the foundation cloth and engaging elements.
Time required for the aforementioned heating is preferably 5 to 15 minutes. The aforementioned heating may be executed just after the hot-melt adhesive is applied. Nevertheless, it is more preferable to heat the surface fastener before the application of the adhesive, because melting time of the hot-melt adhesive is reduced so as to increase finishing speed. The surface fastener finished in this way can be provided with softness and the adhesive can be applied effectively because the amount of the hot-melt adhesive applied can be controlled easily, and engaging elements and the foundation cloth made of knitted/woven fabric or nonwoven fabric can be fixed effectively by the adhesive. Consequently, a sewing thread can be pierced easily in sewing process, so that stability of the sewing operation is secured.
Further, because the powdery hot-melt adhesive is applied from the engaging element formation face side of the surface fastener, the entangling portions between the engaging elements and the foundation cloth and the entangling portions of yarns or fibers of the foundation cloth can be fixed accurately without allowing hot-melt adhesive to adhere to the engaging elements. Consequently, even if the skin touches the engaging elements, it does not feel rough and moreover, the engagement/disengagement is not disturbed. The present invention is applicable not only to the surface fastener having the engaging elements on both the front and rear faces of the foundation cloth but also to an ordinary surface fastener having the engaging elements on a single side of the foundation cloth.
Further, in the present invention, it is preferable to charge at least the foundation cloth of the surface fastener when the hot-melt adhesive is applied. Because the surface fastener which is a finishing object of the present invention is composed of synthetic fiber material, it is easily charged by friction. Therefore, the surface fastener is charged before it reaches the finishing process of the present invention during it passes a number of steps. On the other hand, the powdery hot-melt adhesive is easily adsorbed to a charged surface fastener because the adhesive is mainly composed of thermoplastic resin. This property enables the powdery hot-melt adhesive to be applied effectively to the surface fastener.
However, because electric charge is not achieved uniformly if the electric charge is executed naturally when the surface fastener is processed, the powdery hot-melt adhesive is never adsorbed equally. Thus, according to the present invention, in order to apply the powdery hot-melt adhesive uniformly to the engaging element formation face of the surface fastener, preferably, the surface fastener is charged uniformly again with a charging means after it is deprived of static electricity temporarily. Consequently, the powdery hot-melt adhesive sprayed from a supply portion can be attached uniformly to a charged region.
Moreover, it is preferable for the present invention to include removal of static electricity of the surface fastener. Although the removal of static electricity may be executed before the aforementioned charging of electricity, it is preferable that static electricity is removed further after charging. If static electricity is removed prior to charging, further uniform charging can be achieved by aggressive charging at a next step. If the powdery hot-melt adhesive is applied at this time, the same adhesive is supplied to the surface fastener uniformly, but it is also adsorbed by the engaging element itself. Thus, when the powdery hot-melt adhesive is melted by heat at following procedures, the adhesive is melted and solidified integrally while adhering to the surface of the engaging elements.
Therefore, if static electricity is removed after the powdery hot-melt adhesive is uniformly adsorbed by aggressive charging, the powder adsorbed by the engaging elements slips down along the surface of the engaging elements, so that the powder gathers around the base portions thereof and at the surface of the foundation cloth. Thus, no adhesive adheres or solidifies on the engaging elements at the time of melting and bonding by the subsequent heating process, so that the engaging elements can obtain smooth surfaces so as to exert their proper functions accurately.
Furthermore, it is preferable for the present invention to include vibrating of the surface fastener during application of said adhesive.
The powdery hot-melt adhesive applied to the surface fastener hardly adheres to the engaging elements even if no special operation is carried out, because it is powdery. However, when the surface fastener is charged as described above, if the surface fastener is vibrated aggressively at the same time of charging, most adhesive adsorbed and left on the surface of the engaging elements slips down to a foundation cloth side. As a result, almost 100% of adhesive is used for fixing the engaging elements and the knitting/weaving structure of the foundation cloth at the time of subsequent melting and bonding process, thereby enabling effective finish work without losing the function of the engaging elements. In the meantime, if static electricity is removed after the surface fastener is charged and adhesive is adsorbed by the surface fastener, the powdery hot-melt adhesive adsorbed by the surface of the engaging elements slips down further effectively by the vibration.
In addition, it is preferable to set the particle size of the hot-melt adhesive 500 xcexcm or less. If the particle size of the hot-melt adhesive exceeds 500 xcexcm, adhesive which does not reach the foundation cloth or the base portions of the engaging elements but is halted halfway appears, so that more adhesive bonds the engaging elements with each other or adheres to the engaging elements and solidifies, thereby affecting the engagement strength. Additionally, fixing strength of the knitting/weaving structure cannot be obtained enough despite of the amount of the adhesive applied.
It is preferable that the main component of the hot-melt adhesive is thermoplastic resin having adhesiveness to both the foundation cloth and the engaging elements.
The hot-melt adhesive is mainly composed of various thermoplastic resins as described above. On the other hand, the component material of the surface fastener is also various: For example, such thermoplastic resins as polyester, polyamide, polyacetal, polypropylene, and polyacrylonitrile are used alone or in combination. When one resin material is used for the surface fastener, hot-melt adhesive whose main component is the same as that of the surface fastener can be used. On the other hand, when different resin materials are used for the surface fastener, it is preferable to employ a hot-melt adhesive, whose main component is a resin having a high affinity with any of the resin materials of the surface fastener.
In the present invention, the engaging elements are formed on both front and rear surfaces of the foundation cloth and the powdery hot-melt adhesive can be applied to at least a formation side surface of the male engaging elements.
According to the basic finish principle of the present invention, as described above, because the hot-melt adhesive is powdery, the hot-melt adhesive can be applied directly to and fix the engaging element formation face of the surface fastener. Therefore, even in a surface fastener having the engaging elements on both the sides of the knitted/woven fabric, the engaging elements and foundation cloth can be fixed from both faces. In this case also, softness of the surface fastener is secured if the amount of the adhesive applied is adjusted, so that the knitting/weaving structure of the foundation cloth and the engaging elements can be fixed sufficiently without losing the piercing performance of a sewing thread.
However, in the fiber surface fastener having the engaging elements on both faces of the foundation cloth, the formation density of hook-like engaging elements composed of monofilament, which are male engaging elements, is generally smaller than the formation density of loop-like engaging elements composed of multi-filament, which are female engaging elements. In addition, because of the structural property of the male engaging elements, they easily disperse powdery hot-melt adhesive on the surface of the foundation cloth compared to a plurality of female loop-like engaging elements. Thus, to the surface fastener which engaging elements are formed on both front and rear faces of the foundation cloth of, powdery hot-melt adhesive is applied at least from the formation face side of the male engaging elements, to which the adhesive easily disperses on the foundation cloth face. As a result, it becomes easy to obtain a desired engagement function of the female loop-like engaging elements composed of multi-filament with the male hook-like engaging elements.
When the engaging elements are formed on a surface of the foundation cloth, the powdery hot-melt adhesive can be applied to the surface on which the engaging elements are formed. In the fiber surface fastener to be finished by applying this adhesive, the entangling portions of component yarns of this foundation cloth and the entangling portions between proximal end portions of the engaging elements and the component yarns of the foundation cloth are fixed at the formation face side of the engaging elements while little adhesive flows out to its opposite face. Thus, it is possible to obtain a fiber surface fastener, which has excellent softness as well as good piercing performance of a sewing thread.
The above-mentioned method can provide a fiber surface fastener including a plurality of engaging elements formed on the foundation cloth composed of knitted/woven cloth or nonwoven cloth, wherein the engaging element formation face of the foundation cloth and the base portions of the engaging elements are bonded and covered with a melted and solidified layer of the powdery hot-melt adhesive applied from the engaging element formation face side.
Such a fiber surface fastener is obtained by applying powdery hot-melt adhesive preliminarily from the engaging element formation face side of the foundation cloth, melting said adhesive by heating, and then bonding and solidifying the adhesive. Thus, even in the surface fastener having the engaging elements on both the front and rear faces, the foundation cloth and the engaging elements can be fixed. Consequently, not only the configuration of the foundation cloth becomes stable but also disengagement of engaging elements is prevented. Further, because the amount of the adhesive applied to the surface fastener can be controlled appropriately, its softness can be secured and the piercing performance of the sewing thread is improved, so as not to impose excessive strain to a sewing machine thereby ensuring durability and achieving a smooth sewing.
Said engaging elements include not only the hook-like engaging elements composed of monofilament and the loop-like engaging elements composed of multi-filament formed by knitting/weaving the monofilament, said hook- and loop-like engaging elements being formed upon ordinal knitting/weaving of the foundation cloth, but also the loop-like engaging element composed of nonwoven fabric component fiber protruded from the surface of nonwoven fabric. When nonwoven fabric is used, although the loop-like engaging elements include a portion which is melted and bonded because the hot-melt adhesive adheres partially, the engaging strength and separation resistance are not lowered a lot, so that they can bear actual use sufficiently.
In the fiber surface fastener, the engaging elements can be formed on both the front and rear faces of the foundation cloth and at least one face thereof can be bonded and covered with melted and solidified layer of the hot-melt adhesive. This structure is achieved only by the vapor-finishing principle of the present invention described above and there is little drop in the engagement performance due to this finish work and further, an original taste as fiber surface fastener is never lost.
Especially, the male engaging element formation face of the foundation cloth can be bonded and covered with melted and solidified layer of the hot-melt adhesive. As described above, the male hook-like engaging elements composed of monofilament have a smaller formation density than the female loop-like engaging elements composed of multi-filament. Further, from viewpoint of the structure, if the powdery hot-melt adhesive is applied from each formation face side, it is more likely to be dispersed on the surface of the foundation cloth when the adhesive is supplied from the male engaging element formation face side. Further, entangling portions between the foundation cloth and the female engaging elements formed on the rear face are exposed on this surface. Therefore, the powdery hot-melt adhesive applied from the side on which the male engaging elements are formed is dispersed effectively on the surface of the foundation cloth which is the proximal end portion of each engaging element, and it is melted and solidified. Therefore, not only the foundation cloth but also entangling portions between the foundation cloth and the male or female engaging elements are fixed firmly, thereby durability being improved.